1. Field of the Invention
The present invention relates to a sub headlight unit and a sub headlight system for use in a vehicle that leans into turns, and a vehicle that leans into turns.
2. Description of the Related Art
In general, in a vehicle that leans into turns (such as saddle-ride type vehicles including motorcycles, three-wheeled motor vehicles, snowmobiles, and ATVs (all terrain vehicles), for example), when the vehicle corners or turns at an intersection, a rider operates a handlebar and additionally shifts his/her own weight in order to counteract centrifugal force acting on a vehicle body. Thereby, the vehicle turns with an attitude (hereinafter, also referred to as “lean attitude”) leaning to the inner side of a curve. On the other hand, in a vehicle that does not lean into turns, for example, in an automobile, when the vehicle corners or turns at an intersection, a rider operates a steering wheel and turns with centrifugal force acting on a vehicle body. Therefore, in the vehicle that does not lean into turns, the vehicle body leans to the outer side of a curve due to the centrifugal force.
In the vehicle that leans into turns, the turning is performed with an active use of weight shifting of the rider himself/herself. Therefore, the vehicle body largely leans. In the vehicle that does not lean into turns, the vehicle body leans to the outer side of the curve due to the centrifugal force. The degree of this leaning varies depending on the running speed of the vehicle and the magnitude (radius) of the curve, and this leaning of the vehicle body is not utilized to perform turning. In the vehicle that does not lean into turns, it is preferable that the amount of leaning to the outer side of the curve due to the centrifugal force is small.
Thus, at a time of cornering or turning at an intersection, the vehicle that leans into turns causes the vehicle body to lean to the inner side of the curve with a relatively large amount of leaning, while the vehicle that does not lean into turns causes the vehicle body to lean to the outer side of the curve with a relatively small amount of leaning.
Normally, a vehicle is provided with a plurality of lights irrespective of whether or not the vehicle leans into turns. The lights include a light intended mainly to ensure a field of view of a rider of the vehicle and a light intended mainly to allow a surrounding vehicle or the like to recognize the presence of the rider's own vehicle. A headlight is the light intended mainly to ensure the field of view of the rider of the vehicle, and in general, is configured to switch between a high beam (running headlight) and a low beam (passing headlight).
The high beam, which emits light in a horizontal (upward) direction, ensures a field of view at a long distance. Generally, in order to avoid blinding or impairing the vision of a rider of a nearby or oncoming vehicle, the high beam is used in a situation where there is no vehicle or the like existing ahead at night. The low beam, which emits light in a downward direction, is used even in a situation where there is a vehicle or the like existing ahead. Therefore, in a normal case, a vehicle often runs with the low beam turned on.
When the vehicle that leans into turns is running on a straight road, an illumination range of a headlight light source (low beam) spreads evenly to the left and right in an area ahead in an advancing direction and below a horizontal plane including the headlight light source. When the vehicle that leans into turns is running on a road curving to the left, the vehicle runs with the vehicle body inclined to the left. Accordingly, the illumination range of the headlight light source spreads downward to the left. As a result, a closer position on a running lane is illuminated. Thus, the illumination range in an area inside the curve and ahead in the advancing direction is reduced.
Therefore, for the purpose of preventing a reduction in the illumination range which may be caused by inclination of the vehicle, a vehicle has been proposed in which, in addition to a main headlight that illuminates an area ahead of the vehicle, two right and left sub headlights that are turned on depending on the magnitude of a lean angle (angle of inclination of a vehicle body to the inner side of a curve relative to an upright state thereof) are provided as a headlight, so that the sub headlights are sequentially turned on along with an increase in the lean angle (See, for example, Japanese Patent No. 4864562).
In the vehicle disclosed in Japanese Patent No. 4864562, when, firstly, the lean angle increases to reach a predetermined value, a first sub headlight is turned on, so that an illumination range of the first sub headlight is added to an illumination range of the main headlight which has been reduced as a result of inclination of the vehicle. When the lean angle further increases to reach a predetermined value, a second sub headlight is turned on, so that an illumination range of the second sub headlight is added to the illumination ranges of the main headlight and the first sub headlight which have been reduced as a result of inclination of the vehicle. This can suppress a reduction in the illumination range which may be caused by inclination of the vehicle.
A situation under which the vehicle corners or turns at an intersection is not always the same, and there are a wide variety of running scenes. The present inventors have studied situations under which the vehicle disclosed in Japanese Patent No. 4864562 runs in a wide variety of scenes, and discovered the following problems.
To be specific, in a state in which the vehicle disclosed in Japanese Patent No. 4864562 is running in such various scenes, when the lean angle of the vehicle body gradually increases or decreases, the illumination range of the sub headlight within a rider's field of view largely changes, which sometimes causes the rider to feel uncomfortable. Moreover, in some cases, a time period occurs during which the illumination range of the sub headlight cannot sufficiently cover a position or area that the rider desires to see.
For example, even on a road having a curve with the same radius, some vehicles move through the curve at a relatively low speed, and other vehicles move through the curve at a relatively high speed. The lean angle of the vehicle passing at the high speed is larger than the lean angle of the vehicle passing at the low speed. That is, even though a vehicle moves through a road having a curve with the same radius, the lean angle varies depending on the vehicle speed.
In the vehicle disclosed in Japanese Patent No. 4864562, a reduction in the illumination range along with an increase in the lean angle is suppressed by turning on the first and second sub headlights. Nevertheless, when the vehicle moves through a road having a curve with the same radius, the illumination range of the sub headlight within the rider's field of view largely changes, which sometimes causes the rider to feel uncomfortable. Moreover, when the vehicle moves through a road having a curve with the same radius, a time period sometimes occurs during which the illumination range of the sub headlight cannot sufficiently cover a position or area that the rider desires to see.
Furthermore, even when the vehicle is running at the same speed, the lean angle is small in a curve with a large radius while the lean angle is large in a curve with a small radius. Accordingly, for example, in a case of continuously passing through a plurality of curves having different radii during touring on a mountain road, the lean angle changes in each curve even though the speed does not change so much.
In the vehicle disclosed in Japanese Patent No. 4864562, a reduction in the illumination range along with an increase in the lean angle is suppressed by turning on the first and second sub headlights. Nevertheless, in some cases, while the vehicle is running at the same speed, the illumination range of the sub headlight within the rider's field of view largely changes, which sometimes causes the rider to feel uncomfortable. Moreover, while the vehicle is running at the same speed, a time period sometimes occurs during which the illumination range of the sub headlight cannot sufficiently cover a position or area that the rider desires to see.
In this manner, in the vehicle disclosed in Japanese Patent No. 4864562, when the vehicle moves through a road having a curve with the same radius at different speeds or when the vehicle moves through different curves at the same speed, the illumination range of the sub headlight within the rider's field of view sometimes largely changes, and a time period sometimes occurs during which the illumination range of the sub headlight cannot sufficiently cover a position or area that the rider desires to see.